Hybrid replicated shared memory

ABSTRACT

A multiple computer system with hybrid replicated shared memory is disclosed. The local memory ( 10, 20, . . . 80 ) of each of the multiple computers M 1 , M 2 , . . . Mn is partitioned into a first part ( 11, 21, . . . 81 ) and a second part ( 12, 22, . . . 82 ). Each of the first parts are identical and each of the second parts are independent. The total memory available to the system is the first memory part plus n times the second memory part, n being the total number of application running multiple computers.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims benefit under 35 USC 119(e) to copendingU.S. Provisional Application Nos. 60/850,537 and 60/850,711, both filed9 Oct. 2006. This application also claims priority under 35 USC119(a)-(d) to Australian Provisional Application Nos. 2006905534 and2006905527, both filed on 5 Oct. 2006, each of which are herebyincorporated herein by reference.

This application is related to concurrently filed U.S. application Ser.No. 11/973,374 entitled “Hybrid Replicated Shared Memory,” nowabandoned, and concurrently filed and allowed U.S. application Ser. No.11/973,373 entitled “Hybrid Replicated Shared Memory,” each of which arehereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to computing and, in particular, to thesimultaneous operation of a plurality of computers interconnected via acommunications network.

BACKGROUND ART

International Patent Application No. PCT/AU2005/000580 published underWO 2005/103926 (to which U.S. patent application Ser. No. 11/111,946 andpublished under No. 2005-0262313 corresponds) in the name of the presentapplicant, discloses how different portions of an application programwritten to execute on only a single computer can be operatedsubstantially simultaneously on a corresponding different one of aplurality of computers. That simultaneous operation has not beencommercially used as of the priority date of the present application.International Patent Application Nos. PCT/AU2005/001641 (WO2006/110,937) to which U.S. patent application Ser. No. 11/259,885entitled: “Computer Architecture Method of Operation for Multi-ComputerDistributed Processing and Co-ordinated Memory and Asset Handling”corresponds and PCT/AU2006/000532 (WO 2006/110,957) both in the name ofthe present applicant and both unpublished as at the priority date ofthe present application, also disclose further details. The contents ofthe specification of each of the abovementioned prior application(s) arehereby incorporated into the present specification by cross referencefor all purposes.

Briefly stated, the abovementioned patent specifications disclose thatat least one application program written to be operated on only a singlecomputer can be simultaneously operated on a number of computers eachwith independent local memory. The memory locations required for theoperation of that program are replicated in the independent local memoryof each computer. On each occasion on which the application programwrites new data to any replicated memory location, that new data istransmitted and stored at each corresponding memory location of eachcomputer. Thus apart from the possibility of transmission delays, eachcomputer has a local memory the contents of which are substantiallyidentical to the local memory of each other computer and are updated toremain so. Since all application programs, in general, read data muchmore frequently than they cause new data to be written, theabovementioned arrangement enables very substantial advantages incomputing speed to be achieved. In particular, the stratagem enables twoor more commodity computers interconnected by a commodity communicationsnetwork to be operated simultaneously running under the applicationprogram written to be executed on only a single computer.

Genesis of the Invention Non-commercial operation of a prototypemultiple computer system indicates that not every machine or computer inthe system utilises or needs to refer to (e.g. have a local copy of)every possible memory location. As a consequence, it is now realisedthat it is possible to operate a multiple computer system without thelocal memory of each machine being identical to every other machine, solong as the local memory of each machine is sufficient for the operationof that machine. That is to say, provided a particular machine does notneed to refer to (for example have a local copy of) some specific memorylocations, then it does not matter that those specific memory locationsare not duplicated in that particular machine.

Briefly, it is known in the prior art that fragmentation is a phenomenonthat leads to inefficiency in many forms of computer storage.Specifically, memory fragmentation is the phenomenon in which memorystorage becomes divided into many small pieces over time. Memoryfragmentation can occur for example when an application allocates anddeallocates (“frees”) regions of memory of varying sizes, therebyleaving the allocated and deallocated regions interspersed. The resultis that, fragmented memory can potentially become effectively unusablebecause it is broken up into many pieces that are not close together.

Non-commercial operation of a multiple computer system prototypeoperating as a replicated shared memory arrangement has unexpectedlyrevealed that an application program operating in such arrangement foran extended period of time (such as for example, hours or even days ofcontinuous operation) is susceptible to fragmentation between thereplicated application memory locations/contents/values and thenon-replicated application memory locations/contents/values of the localallocated application memories of each member machine making up thereplicated shared memory arrangement.

It has further been revealed through operation of the abovementionedprototype that replicated memory locations/contents/values often “live”far longer on average than unreplicated application memorylocations/contents/values. For example, replicated application memorylocations/contents/values typically take the form of shared datastructures and/or shared contents and/or shared values between pluralthreads of the application program, such as for example queues, lists,shared caches, and the like. Typically, such shared data structuresand/or shared contents and/or shared values persist beyond the averagelife-cycle (duration) of single threads. Un-replicated applicationmemory locations/contents/values, however, are characterised as notbeing shared between plural threads (for example, thread-local storage,thread-local variables, and other thread-private data structures etc),and therefore such un-replicated application memorylocations/contents/values typically do not persist beyond the averagelife-cycle (duration) of a single thread.

The consequences of the above described differing characteristics ofreplicated application memory locations/contents and non-replicatedapplication memory locations/contents leads to wide-spread fragmentationof the allocated application memory between the replicated applicationmemory location/contents and the non-replicated application memorylocations/contents. The problem of “fragmentation” of allocatedapplication memory manifests in numerous ways, such as for exampledelayed or slow memory initialisation/allocation time, reduced effectiveapplication memory capacity, and decreased efficiency in serialising andde-serialising the contents of transmission and receipt of replicamemory update transmissions due to replicated memory locations beingstored in a non-contiguous and fragmented manner.

Investigation has revealed that the above described fragmentationproblems arise due to the manner in which local replica applicationmemory locations/contents/values are allocated or stored to theallocated application memory of individual machines. When replicatedapplication memory contents/values are stored to allocated applicationmemory in an uncoordinated and/or un-organised manner, or when prior artallocation and/or storage arrangements of single independent machinesare used, fragmentation of allocated application memory will typicallyresult when operated in a replicated shared memory arrangement. As atthe priority date, no specific allocation and/or storage arrangement ofreplicated application memory locations/contents/values for multiplecomputer system of a replicated shared memory arrangement is known thatreduces or minimises the incidences of fragmentation between replicatedapplication memory locations/contents/values and non-replicatedapplication memory locations/contents/values for “long-running”replicated shared memory systems.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there isdisclosed a multiple computer system with replicated shared memory, saidsystem comprising a multiplicity of computers each interconnected via acommunications network and each executing a different portion of anapplications program written to be executed on only a single computer,wherein each said computer has an independent local memory partitionedinto two regions, a first one of said regions being substantiallysimilar with corresponding memory content replicated on at least oneother computer, and the second of said regions not corresponding to eachother.

In accordance with a second aspect of the present invention there isdisclosed a method of partitioning an independent local memory of eachcomputer of a multiple computer system comprising a multiplicity ofcomputers each interconnected via a communications system and eachexecuting a different portion of an applications program written to beexecuted on only a single computer, said method comprising the step of:(i) for each said computer partitioning the independent local memoryinto two regions, a first one of said regions being substantiallysimilar with corresponding memory content replicated on at least oneother computer, and the second of said regions not corresponding to eachother.

In accordance with a third aspect of the present invention there isdisclosed a single computer for operation in cooperation with anexternal multiple computer system with replicated shared memory, saidsystem comprising a multiplicity of single computers each interconnectedvia a communications network and each executing a different portion ofan applications program written to be executed on only a singlecomputer, wherein each said single computer has an independent localmemory partitioned into two regions, a first one of said regions beingsubstantially similar with corresponding memory content replicated on atleast one other computer, and the second of said regions notcorresponding to each other.

In accordance with a fourth aspect of the present invention there isdisclosed a method of partitioning local memory of a single computeroperating in cooperation with a multiple computer system comprising amultiplicity of computers each interconnected via a communicationsnetwork and each executing a different portion of an applicationsprogram written to be executed on only a single computer, said methodcomprising the step of: (i) partitioning the local memory of said singlecomputer in two regions, a first one of said regions being substantiallysimilar with corresponding memory content replicated on at least oneother of said computers in the multiple computer system, and the secondof said regions not corresponding to each other.

In accordance with a fifth aspect of the present invention there isdisclosed a multiple computer system with replicated shared memory, saidsystem comprising a multiplicity of computers each interconnected via acommunications network and each executing a different portion of anapplications program written to be executed on only a single computer,wherein each said computer has an independent local memory partitionedinto an allocated application memory, said allocated application memoryfurther partitioned into two regions, a first one of said regionscomprising application memory contents replicated on at least one otherof said computers and updated to remain substantially similar, and thesecond of said regions comprising application memory contents notreplicated on any other of said computers and not updated to remainsubstantially similar.

In accordance with a sixth aspect of the present invention there isdisclosed a method of partitioning an independent local memory of eachcomputer of a multiple computer system comprising a multiplicity ofcomputers each interconnected via a communications system and eachexecuting a different portion of an applications program written to beexecuted on only a single computer, said method comprising the step of:(i) for each said computer partitioning the independent local memoryinto an allocated application memory, said allocated application memoryfurther partitioned into two regions, a first one of said regionscomprising application memory contents replicated on at least one otherof said computers and updated to remain substantially similar, and thesecond of said regions comprising application memory contents notreplicated on any other of said computers and not updated to remainsubstantially similar.

In accordance with a seventh aspect of the present invention there isdisclosed a single computer for operation in cooperation with anexternal multiple computer system with replicated shared memory, saidsystem comprising a multiplicity of single computers each interconnectedvia a communications network and each executing a different portion ofan applications program written to be executed on only a singlecomputer, wherein each said single computer has an independent localmemory partitioned into an allocated application memory, said allocatedapplication memory further partitioned into two regions, a first one ofsaid regions comprising application memory contents replicated on atleast one other of said computers and updated to remain substantiallysimilar, and the second of said regions comprising application memorycontents not replicated on any other of said computers and not updatedto remain substantially similar.

In accordance with a eighth aspect of the present invention there isdisclosed a method of partitioning local memory of a single computeroperating in cooperation with a multiple computer system comprising amultiplicity of computers each interconnected via a communicationsnetwork and each with an independent local memory and each executing adifferent portion of an applications program written to be executed ononly a single computer, said method comprising the step of: (i)partitioning the local memory of said single computer into an allocatedapplication memory, said allocated application memory furtherpartitioned into two regions, a first one of said regions comprisingapplication memory contents replicated on at least one other of saidcomputers and updated to remain substantially similar, and the second ofsaid regions comprising application memory contents not replicated onany other of said computers and not updated to remain substantiallysimilar.

Thus the present invention discloses a beneficial method of storing andallocating replicated application memory locations/contents/values so asto substantially avoid or reduce fragmentation of the allocatedapplication memory between replicated application memorylocations/contents/values and non-replicated application memorylocations/contents/values, of each machine.

Specifically, the present invention discloses a beneficial memorystorage, memory layout, and memory allocation arrangement for replicatedand non-replicated application memory contents and/or application memoryvalues of a single application program being substantiallysimultaneously executed by a plurality of computers operating as areplicated shared memory arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be describedwith reference to the drawings in which:

FIG. 1A is a schematic illustration of a prior art computer arranged tooperate JAVA code and thereby constitute a single JAVA virtual machine,

FIG. 1B is a drawing similar to FIG. 1A but illustrating the initialloading of code,

FIG. 1C illustrates the interconnection of a multiplicity of computerseach being a JAVA virtual machine to form a multiple computer system,

FIG. 2 schematically illustrates “n” application running computers towhich at least one additional server machine X is connected as a server,

FIG. 2A is a schematic diagram of a replicated shared memory system,

FIG. 2B is an illustration of a partial or hybrid RSM system,

FIG. 2C is a diagram similar to that of FIG. 2B but of a partial orhybrid RSM system having five computers,

FIG. 2D illustrates a single physical machine providing several virtualmachines,

FIG. 3 illustrates fragmented memory within a single machine, and

FIGS. 4-6 are each a schematic representation of the memory system ofthe preferred embodiment utilised in a multiple computer system.

DETAILED DESCRIPTION

The embodiments will be described with reference to the JAVA language,however, it will be apparent to those skilled in the art that theinvention is not limited to this language and, in particular can be usedwith other languages (including procedural, declarative and objectoriented languages) including the MICROSOFT.NET platform andarchitecture (Visual Basic, Visual C, and Visual C++, and Visual C#),FORTRAN, C, C++, COBOL, BASIC and the like.

It is known in the prior art to provide a single computer or machine(produced by any one of various manufacturers and having an operatingsystem (or equivalent control software or other mechanism) operating inany one of various different languages) utilizing the particularlanguage of the application by creating a virtual machine as illustratedin FIG. 1A.

The code and data and virtual machine configuration or arrangement ofFIG. 1A takes the form of the application code 50 written in the JAVAlanguage and executing within the JAVA virtual machine 61. Thus wherethe intended language of the application is the language JAVA, a JAVAvirtual machine is used which is able to operate code in JAVAirrespective of the machine manufacturer and internal details of thecomputer or machine. For further details, see “The JAVA Virtual MachineSpecification” 2^(nd) Edition by T. Lindholm and F. Yellin of SunMicrosystems Inc of the USA which is incorporated herein by reference.

This conventional art arrangement of FIG. 1A is modified by the presentapplicant by the provision of an additional facility which isconveniently termed a “distributed run time” or a “distributed run timesystem” DRT 71 and as seen in FIG. 1B.

In FIGS. 1B and 1C, the application code 50 is loaded onto the JavaVirtual Machine(s) M1, M2, . . . Mn in cooperation with the distributedruntime system 71, through the loading procedure indicated by arrow 75or 75A or 75B. As used herein the terms “distributed runtime” and the“distributed run time system” are essentially synonymous, and by meansof illustration but not limitation are generally understood to includelibrary code and processes which support software written in aparticular language running on a particular platform. Additionally, adistributed runtime system may also include library code and processeswhich support software written in a particular language running within aparticular distributed computing environment. A runtime system (whethera distributed runtime system or not) typically deals with the details ofthe interface between the program and the operating system such assystem calls, program start-up and termination, and memory management.For purposes of background, a conventional Distributed ComputingEnvironment (DCE) (that does not provide the capabilities of theinventive distributed run time or distributed run time system 71 used inthe preferred embodiments of the present invention) is available fromthe Open Software Foundation. This Distributed Computing Environment(DCE) performs a form of computer-to-computer communication for softwarerunning on the machines, but among its many limitations, it is not ableto implement the desired modification or communication operations. Amongits functions and operations the preferred DRT 71 coordinates theparticular communications between the plurality of machines M1, M2, . .. Mn. Moreover, the preferred distributed runtime 71 comes intooperation during the loading procedure indicated by arrow 75A or 75B ofthe JAVA application 50 on each JAVA virtual machine 72 or machinesJVM#1, JVM#2, . . . JVM#n of FIG. 1C. It will be appreciated in light ofthe description provided herein that although many examples anddescriptions are provided relative to the JAVA language and JAVA virtualmachines so that the reader may get the benefit of specific examples,there is no restriction to either the JAVA language or JAVA virtualmachines, or to any other language, virtual machine, machine oroperating environment.

FIG. 1C shows in modified form the arrangement of the JAVA virtualmachines, each as illustrated in FIG. 1B. It will be apparent that againthe same application code 50 is loaded onto each machine M1, M2 . . .Mn. However, the communications between each machine M1, M2 . . . Mn areas indicated by arrows 83, and although physically routed through themachine hardware, are advantageously controlled by the individual DRT's71/1 . . . 71/n within each machine. Thus, in practice this may beconceptionalised as the DRT's 71/1, . . . 71/n communicating with eachother via the network or other communications link 53 rather than themachines M1, M2 . . . Mn communicating directly themselves or with eachother. Contemplated and included are either this direct communicationbetween machines M1, M2 . . . Mn or DRT's 71/1, 71/2 . . . 71/n or acombination of such communications. The preferred DRT 71 providescommunication that is transport, protocol, and link independent.

The one common application program or application code 50 and itsexecutable version (with likely modification) is simultaneously orconcurrently executing across the plurality of computers or machines M1,M2 . . . Mn. The application program 50 is written to execute on asingle machine or computer (or to operate on the multiple computersystem of the abovementioned patent applications which emulate singlecomputer operation). Essentially the modified structure is to replicatean identical memory structure and contents on each of the individualmachines.

The term “common application program” is to be understood to mean anapplication program or application program code written to operate on asingle machine, and loaded and/or executed in whole or in part on eachone of the plurality of computers or machines M1, M2 . . . Mn, oroptionally on each one of some subset of the plurality of computers ormachines M1, M2 . . . Mn. Put somewhat differently, there is a commonapplication program represented in application code 50. This is either asingle copy or a plurality of identical copies each individuallymodified to generate a modified copy or version of the applicationprogram or program code. Each copy or instance is then prepared forexecution on the corresponding machine. At the point after they aremodified they are common in the sense that they perform similaroperations and operate consistently and coherently with each other. Itwill be appreciated that a plurality of computers, machines, informationappliances, or the like implementing the above described arrangementsmay optionally be connected to or coupled with other computers,machines, information appliances, or the like that do not implement theabove described arrangements.

The same application program 50 (such as for example a parallel mergesort, or a computational fluid dynamics application or a data miningapplication) is run on each machine, but the executable code of thatapplication program is modified on each machine as necessary such thateach executing instance (copy or replica) on each machine coordinatesits local operations on that particular machine with the operations ofthe respective instances (or copies or replicas) on the other machinessuch that they function together in a consistent, coherent andcoordinated manner and give the appearance of being one global instanceof the application (i.e. a “meta-application”).

The copies or replicas of the same or substantially the same applicationcodes, are each loaded onto a corresponding one of the interoperatingand connected machines or computers. As the characteristics of eachmachine or computer may differ, the application code 50 may be modifiedbefore loading, or during the loading process, or with somedisadvantages after the loading process, to provide a customization ormodification of the application code on each machine. Some dissimilaritybetween the programs or application codes on the different machines maybe permitted so long as the other requirements for interoperability,consistency, and coherency as described herein can be maintained. As itwill become apparent hereafter, each of the machines M1, M2 . . . Mn andthus all of the machines M1, M2 . . . Mn have the same or substantiallythe same application code 50, usually with a modification that may bemachine specific.

Before the loading of, or during the loading of, or at any timepreceding the execution of, the application code 50 (or the relevantportion thereof) on each machine M1, M2 . . . Mn, each application code50 is modified by a corresponding modifier 51 according to the samerules (or substantially the same rules since minor optimizing changesare permitted within each modifier 51/1, 51/2 . . . 51/n).

Each of the machines M1, M2 . . . Mn operates with the same (orsubstantially the same or similar) modifier 51 (in some embodimentsimplemented as a distributed run time or DRT71 and in other embodimentsimplemented as an adjunct to the application code and data 50, and alsoable to be implemented within the JAVA virtual machine itself). Thus allof the machines M1, M2 . . . Mn have the same (or substantially the sameor similar) modifier 51 for each modification required. A differentmodification, for example, may be required for memory management andreplication, for initialization, for finalization, and/or forsynchronization (though not all of these modification types may berequired for all arrangements).

There are alternative implementations of the modifier 51 and thedistributed run time 71. For example, as indicated by broken lines inFIG. 1C, the modifier 51 may be implemented as a component of or withinthe distributed run time 71, and therefore the DRT 71 may implement thefunctions and operations of the modifier 51. Alternatively, the functionand operation of the modifier 51 may be implemented outside of thestructure, software, firmware, or other means used to implement the DRT71 such as within the code and data 50, or within the JAVA virtualmachine itself. In one embodiment, both the modifier 51 and DRT 71 areimplemented or written in a single piece of computer program code thatprovides the functions of the DRT and modifier. In this case themodifier function and structure is, in practice, subsumed into the DRT.Independent of how it is implemented, the modifier function andstructure is responsible for modifying the executable code of theapplication code program, and the distributed run time function andstructure is responsible for implementing communications between andamong the computers or machines. The communications functionality in oneembodiment is implemented via an intermediary protocol layer within thecomputer program code of the DRT on each machine. The DRT can, forexample, implement a communications stack in the JAVA language and usethe Transmission Control Protocol/Internet Protocol (TCP/IP) to providefor communications or talking between the machines. These functions oroperations may be implemented in a variety of ways, and it will beappreciated in light of the description provided herein that exactly howthese functions or operations are implemented or divided betweenstructural and/or procedural elements, or between computer program codeor data structures, is not important or crucial.

However, in the arrangement illustrated in FIG. 1C, a plurality ofindividual computers or machines M1, M2 . . . Mn are provided, each ofwhich are interconnected via a communications network 53 or othercommunications link. Each individual computer or machine is providedwith a corresponding modifier 51. Each individual computer is alsoprovided with a communications port which connects to the communicationsnetwork. The communications network 53 or path can be any electronicsignalling, data, or digital communications network or path and ispreferably a slow speed, and thus low cost, communications path, such asa network connection over the Internet or any common networkingconfigurations including ETHERNET or INFINIBAND and extensions andimprovements, thereto. Preferably, the computers are provided with oneor more known communications ports (such as CISCO Power Connect 5224Switches) which connect with the communications network 53.

As a consequence of the above described arrangement, if each of themachines M1, M2, . . . , Mn has, say, an internal or local memorycapability of 10 MB, then the total memory available to the applicationcode 50 in its entirety is not, as one might expect, the number ofmachines (n) times 10 MB. Nor is it the additive combination of theinternal memory capability of all n machines. Instead it is either 10MB, or some number greater than 10 MB but less than n×10 MB. In thesituation where the internal memory capacities of the machines aredifferent, which is permissible, then in the case where the internalmemory in one machine is smaller than the internal memory capability ofat least one other of the machines, then the size of the smallest memoryof any of the machines may be used as the maximum memory capacity of themachines when such memory (or a portion thereof) is to be treated as‘common’ memory (i.e. similar equivalent memory on each of the machinesM1 . . . Mn) or otherwise used to execute the common application code.

However, even though the manner that the internal memory of each machineis treated may initially appear to be a possible constraint onperformance, how this results in improved operation and performance willbecome apparent hereafter. Naturally, each machine M1, M2 . . . Mn has aprivate (i.e. ‘non-common’) internal memory capability. The privateinternal memory capability of the machines M1, M2, . . . , Mn arenormally approximately equal but need not be. For example, when amultiple computer system is implemented or organized using existingcomputers, machines, or information appliances, owned or operated bydifferent entities, the internal memory capabilities may be quitedifferent. On the other hand, if a new multiple computer system is beingimplemented, each machine or computer is preferably selected to have anidentical internal memory capability, but this need not be so.

It is to be understood that the independent local memory of each machinerepresents only that part of the machine's total memory which isallocated to that portion of the application program running on thatmachine. Thus, other memory will be occupied by the machine's operatingsystem and other computational tasks unrelated to the applicationprogram 50.

Non-commercial operation of a prototype multiple computer systemindicates that not every machine or computer in the system utilises orneeds to refer to (e.g. have a local replica of) every possible memorylocation. As a consequence, it is possible to operate a multiplecomputer system without the local memory of each machine being identicalto every other machine, so long as the local memory of each machine issufficient for the operation of that machine. That is to say, provided aparticular machine does not need to refer to (for example have a localreplica of) some specific memory locations, then it does not matter thatthose specific memory locations are not replicated in that particularmachine.

It may also be advantageous to select the amounts of internal memory ineach machine to achieve a desired performance level in each machine andacross a constellation or network of connected or coupled plurality ofmachines, computers, or information appliances M1, M2, . . . , Mn.Having described these internal and common memory considerations, itwill be apparent in light of the description provided herein that theamount of memory that can be common between machines is not alimitation.

In some arrangements, some or all of the plurality of individualcomputers or machines can be contained within a single housing orchassis (such as so-called “blade servers” manufactured byHewlett-Packard Development Company, Intel Corporation, IBM Corporationand others) or the multiple processors (eg symmetric multiple processorsor SMPs) or multiple core processors (eg dual core processors and chipmultithreading processors) manufactured by Intel, AMD, or others, orimplemented on a single printed circuit board or even within a singlechip or chipset. Similarly, also included are computers or machineshaving multiple cores, multiple CPU's or other processing logic.

When implemented in a non-JAVA language or application code environment,the generalized platform, and/or virtual machine and/or machine and/orruntime system is able to operate application code 50 in the language(s)(possibly including for example, but not limited to any one or more ofsource-code languages, intermediate-code languages, object-codelanguages, machine-code languages, and any other code languages) of thatplatform and/or virtual machine and/or machine and/or runtime systemenvironment, and utilize the platform, and/or virtual machine and/ormachine and/or runtime system and/or language architecture irrespectiveof the machine or processor manufacturer and the internal details of themachine. It will also be appreciated that the platform and/or runtimesystem can include virtual machine and non-virtual machine softwareand/or firmware architectures, as well as hardware and direct hardwarecoded applications and implementations.

For a more general set of virtual machine or abstract machineenvironments, and for current and future computers and/or computingmachines and/or information appliances or processing systems, and thatmay not utilize or require utilization of either classes and/or objects,the structure, method and computer program and computer program productare still applicable. Examples of computers and/or computing machinesthat do not utilize either classes and/or objects include for example,the x86 computer architecture manufactured by Intel Corporation andothers, the SPARC computer architecture manufactured by SunMicrosystems, Inc and others, the Power PC computer architecturemanufactured by International Business Machines Corporation and others,and the personal computer products made by Apple Computer, Inc., andothers.

For these types of computers, computing machines, informationappliances, and the virtual machine or virtual computing environmentsimplemented thereon that do not utilize the idea of classes or objects,may be generalized for example to include primitive data types (such asinteger data types, floating point data types, long data types, doubledata types, string data types, character data types and Boolean datatypes), structured data types (such as arrays and records), derivedtypes, or other code or data structures of procedural languages or otherlanguages and environments such as functions, pointers, components,modules, structures, reference and unions. These structures andprocedures when applied in combination when required, maintain acomputing environment where memory locations, address ranges, objects,classes, assets, resources, or any other procedural or structural aspectof a computer or computing environment are where required created,maintained, operated, and deactivated or deleted in a coordinated,coherent, and consistent manner across the plurality of individualmachines M1, M2 . . . Mn.

This analysis or scrutiny of the application code 50 can take placeeither prior to loading the application program code 50, or during theapplication program code 50 loading procedure, or even after theapplication program code 50 loading procedure (or some combination ofthese). It may be likened to an instrumentation, program transformation,translation, or compilation procedure in that the application code canbe instrumented with additional instructions, and/or otherwise modifiedby meaning-preserving program manipulations, and/or optionallytranslated from an input code language to a different code language(such as for example from source-code language or intermediate-codelanguage to object-code language or machine-code language). In thisconnection it is understood that the term “compilation” normally orconventionally involves a change in code or language, for example, fromsource code to object code or from one language to another language.However, in the present instance the term “compilation” (and itsgrammatical equivalents) is not so restricted and can also include orembrace modifications within the same code or language. For example, thecompilation and its equivalents are understood to encompass bothordinary compilation (such as for example by way of illustration but notlimitation, from source-code to object code), and compilation fromsource-code to source-code, as well as compilation from object-code toobject code, and any altered combinations therein. It is also inclusiveof so-called “intermediary-code languages” which are a form of “pseudoobject-code”.

By way of illustration and not limitation, in one arrangement, theanalysis or scrutiny of the application code 50 takes place during theloading of the application program code such as by the operating systemreading the application code 50 from the hard disk or other storagedevice, medium or source and copying it into memory and preparing tobegin execution of the application program code. In another arrangement,in a JAVA virtual machine, the analysis or scrutiny may take placeduring the class loading procedure of thejava.lang.ClassLoader.loadClass method (e.g.“java.lang.ClassLoader.loadClass( )”).

Alternatively, or additionally, the analysis or scrutiny of theapplication code 50 (or of a portion of the application code) may takeplace even after the application program code loading procedure, such asafter the operating system has loaded the application code into memory,or optionally even after execution of the relevant corresponding portionof the application program code has started, such as for example afterthe JAVA virtual machine has loaded the application code into thevirtual machine via the “java.lang.ClassLoader.loadClass( )” method andoptionally commenced execution.

Persons skilled in the computing arts will be aware of various possibletechniques that may be used in the modification of computer code,including but not limited to instrumentation, program transformation,translation, or compilation means and/or methods.

One such technique is to make the modification(s) to the applicationcode, without a preceding or consequential change of the language of theapplication code. Another such technique is to convert the original code(for example, JAVA language source-code) into an intermediaterepresentation (or intermediate-code language, or pseudo code), such asJAVA byte code. Once this conversion takes place the modification ismade to the byte code and then the conversion may be reversed. Thisgives the desired result of modified JAVA code.

A further possible technique is to convert the application program tomachine code, either directly from source-code or via the abovementionedintermediate language or through some other intermediate means. Then themachine code is modified before being loaded and executed. A stillfurther such technique is to convert the original code to anintermediate representation, which is thus modified and subsequentlyconverted into machine code. All such modification routes are envisagedand also a combination of two, three or even more, of such routes.

The DRT 71 or other code modifying means is responsible for creating orreplicating a memory structure and contents on each of the individualmachines M1, M2 . . . Mn that permits the plurality of machines tointeroperate. In some arrangements this replicated memory structure willbe identical. Whilst in other arrangements this memory structure willhave portions that are identical and other portions that are not. Instill other arrangements the memory structures are different only informat or storage conventions such as Big Endian or Little Endianformats or conventions.

These structures and procedures when applied in combination whenrequired, maintain a computing environment where the memory locations,address ranges, objects, classes, assets, resources, or any otherprocedural or structural aspect of a computer or computing environmentare where required created, maintained, operated, and deactivated ordeleted in a coordinated, coherent, and consistent manner across theplurality of individual machines M1, M2 . . . Mn.

Therefore the terminology “one”, “single”, and “common” application codeor program includes the situation where all machines M1, M2 . . . Mn areoperating or executing the same program or code and not different (andunrelated) programs, in other words copies or replicas of same orsubstantially the same application code are loaded onto each of theinteroperating and connected machines or computers.

In conventional arrangements utilising distributed software, memoryaccess from one machine's software to memory physically located onanother machine typically takes place via the network interconnectingthe machines. Thus, the local memory of each machine is able to beaccessed by any other machine and can therefore cannot be said to beindependent. However, because the read and/or write memory access tomemory physically located on another computer require the use of theslow network interconnecting the computers, in these configurations suchmemory accesses can result in substantial delays in memory read/writeprocessing operations, potentially of the order of 10⁶-10⁷ cycles of thecentral processing unit of the machine (given contemporary processorspeeds). Ultimately this delay is dependent upon numerous factors, suchas for example, the speed, bandwidth, and/or latency of thecommunication network. This in large part accounts for the diminishedperformance of the multiple interconnected machines in the prior artarrangement.

However, in the present arrangement all reading of memory locations ordata is satisfied locally because a current value of all (or some subsetof all) memory locations is stored on the machine carrying out theprocessing which generates the demand to read memory.

Similarly, all writing of memory locations or data is satisfied locallybecause a current value of all (or some subset of all) memory locationsis stored on the machine carrying out the processing which generates thedemand to write to memory.

Such local memory read and write processing operation can typically besatisfied within 10²-10³ cycles of the central processing unit. Thus, inpractice there is substantially less waiting for memory accesses whichinvolves and/or writes. Also, the local memory of each machine is notable to be accessed by any other machine and can therefore be said to beindependent.

The arrangement is transport, network, and communications pathindependent, and does not depend on how the communication betweenmachines or DRTs takes place. Even electronic mail (email) exchangesbetween machines or DRTs may suffice for the communications.

In connection with the above, it will be seen from FIG. 2 that there area number of machines M1, M2, . . . Mn, “n” being an integer greater thanor equal to two, on which the application program 50 of FIG. 1 is beingrun substantially simultaneously. These machines are allocated a number1, 2, 3, . . . etc. in a hierarchical order. This order is normallylooped or closed so that whilst machines 2 and 3 are hierarchicallyadjacent, so too are machines “n” and 1. There is preferably a furthermachine X which is provided to enable various housekeeping functions tobe carried out, such as acting as a lock server. In particular, thefurther machine X can be a low value machine, and much less expensivethan the other machines which can have desirable attributes such asprocessor speed. Furthermore, an additional low value machine (X+1) ispreferably available to provide redundancy in case machine X shouldfail. Where two such server machines X and X+1 are provided, they arepreferably, for reasons of simplicity, operated as dual machines in acluster configuration. Machines X and X+1 could be operated as amultiple computer system in accordance with the above describedarrangement, if desired. However this would result in generallyundesirable complexity. If the machine X is not provided then itsfunctions, such as housekeeping functions, are provided by one, or some,or all of the other machines.

In FIG. 2A three machines are shown, of a total of “n” machines (n beingan integer greater than one) that is machines M1, M2, . . . Mn.Additionally, a communications network 53 is shown interconnecting thethree machines and a preferable (but optional) server machine X whichcan also be provided and which is indicated by broken lines. In each ofthe individual machines, there exists a memory 2A102 and a CPU 2A103. Ineach memory 2A102 there exists three memory locations, a memory locationA, a memory location B, and a memory location C. Each of these threememory locations is replicated in a memory 2A102 of each machine.

This arrangement of the replicated shared memory system allows a singleapplication program written for, and intended to be run on, a singlemachine, to be substantially simultaneously executed on a plurality ofmachines, each with independent local memories, accessible only by thecorresponding portion of the application program executing on thatmachine, and interconnected via the network 53. In International PatentApplication No. PCT/AU2005/001641 to which U.S. patent application Ser.No. 11/259,885 entitled: “Computer Architecture Method of Operation forMulti-Computer Distributed Processing and Co-ordinated Memory and AssetHandling” corresponds and PCT/AU2006/000532 in the name of the presentapplicant, a technique is disclosed to detect modifications ormanipulations made to a replicated memory location, such as a write to areplicated memory location A by machine M1 and correspondingly propagatethis changed value written by machine M1 to the other machines M2 . . .Mn which each have a local replica of memory location A. This result isachieved by the preferred embodiment of detecting write instructions inthe executable object code of the application to be run that write to areplicated memory location, such as memory location A, and modifying theexecutable object code of the application program, at the pointcorresponding to each such detected write operation, such that newinstructions are inserted to additionally record, mark, tag, or by somesuch other recording means indicate that the value of the written memorylocation has changed.

An alternative arrangement is that illustrated in FIG. 2B and termedpartial or hybrid replicated shared memory (RSM). Here memory location Ais replicated on computers or machines M1 and M2, memory location B isreplicated on machines M1 and Mn, and memory location C is replicated onmachines M1, M2 and Mn. However, the memory locations D and E arepresent only on machine M1, the memory locations F and G are presentonly on machine M2, and the memory locations Y and Z are present only onmachine Mn. Such an arrangement is disclosed in International PatentApplication No. PCT/AU2006/001447 published under WO 2007/041762 (and towhich U.S. patent application Ser. No. 11/583,958). In such a partial orhybrid RSM systems changes made by one computer to memory locationswhich are not replicated on any other computer do not need to be updatedat all. Furthermore, a change made by any one computer to a memorylocation which is only replicated on some computers of the multiplecomputer system need only be propagated or updated to those somecomputers (and not to all other computers).

Consequently, for both RSM and partial RSM, a background thread task orprocess is able to, at a later stage, propagate the changed value to theother machines which also replicate the written to memory location, suchthat subject to an update and propagation delay, the memory contents ofthe written to memory location on all of the machines on which a replicaexists, are substantially identical. Various other alternativeembodiments are also disclosed in the abovementioned prior art. Whilstthe above prior art methods are adequate for application programs whichwrite infrequently to replicated memory locations, the prior art methodis prone to inherent inefficiencies in those application programs whichwrite frequently to replicated memory locations.

All described embodiments and arrangements of the present invention areequally applicable to replicated shared memory systems, whetherpartially replicated or not. Specifically, partially replicated sharedmemory arrangements where some plurality of memory locations arereplicated on some subset of the total machines operating in thereplicated shared memory arrangement, themselves may constitute areplicated shared memory arrangement for the purposes of this invention.

All described embodiments and arrangements of the present invention areequally applicable to replicated shared memory systems, whetherpartially replicated or not. Specifically, partially replicated sharedmemory arrangements where some plurality of memory locations arereplicated on some subset of the total machines operating in thereplicated shared memory arrangement, themselves may constitute areplicated shared memory arrangement for the purposes of this invention.

With reference to FIG. 2C, where memory locations “A”, “B”, and “C” arereplicated on three machines M1, M2, and M3 of a five machine replicatedshared memory arrangement (comprising additional machines M4 and M5),then for the purposes of this invention the term replicated sharedmemory arrangement is not to be restricted to all 5 machines M1-M5, butmay be also encompass any lesser plurality of machines (less than thetotal number of machines) in the operating arrangement, such as forexample machines M1-M3. Thus, machines M1, M2 and M3 with replicatedmemory locations “A”, “B” and “C” constitute a replicated shared memoryarrangement in their own right (without machines M4 or M5).

Typically, the embodiments of replicated shared memory arrangementsdescribed and illustrated herein generally are made up from a pluralityof independent machines with independent local memories such as thatdepicted in FIGS. 2A, 2B, and 2C. However, various alternative machinearrangements constituting a replicated shared memory system are providedby, and are included within the scope of, this invention.

Specifically, the term “machine” used herein to refer to a singularcomputing entity of a plurality of such entities operating as areplicated shared memory arrangement is not to be restricted or limitedto mean only a single physical machine or other single computer system.Instead, the use of the term “machine” herein is to be understood toencompass and include within its scope a more broad usage for any“replicated memory instance” (or “replicated memory image”, or“replicated memory unit”) of a replicated shared memory arrangement.

Specifically, replicated shared memory arrangements as described hereininclude a plurality of machines, each of which operates with anindependent local memory. Each such independent local memory of aparticipating machine within a replicated shared memory arrangementrepresents an “independent replicated memory instance” (whetherpartially replicated or fully replicated). That is, the local memory ofeach machine in a plurality of such machines operating as a replicatedshared memory arrangement, represents and operates as an “independentreplicated memory instance”. Whilst the most common embodiment of such a“replicated memory instance” is a single such instance of a singlephysical machine forming some subset, or total of, the local memory ofthat single physical machine, “replicated memory instances” are notlimited to such single physical machine arrangements only.

For example, it is provided by this invention to include within itsscope any of various “virtual machine” or similar arrangements. Onegeneral example of a “virtual machine” arrangement is indicated in FIG.2D. Such virtual machine arrangements may take the form of hypervisor orvirtual machine monitor assisted arrangements such as VMWare virtualmachine instances, or Xen paravirtualization instances. Alternativesubstantially equivalent virtual machine arrangements also includeSolaris Containers, Isolated Software Domains, Parallel Operating Systeminstances, substantially independent Application Processes or Tasks withindependent and/or isolated and/or protected memories, or any other suchindependent virtual machine instance or such similar multi-programarrangement with an independent or isolated or protected memory. Thoseskilled in the computing arts will be familiar with various alternative“virtual machine” arrangements.

Utilising any of the various “virtual machine” arrangements, multiple“virtual machines” may reside on, or occupy, a single physical machine,and yet operate in a substantially independent manner with respect tothe methods of this invention and the replicated shared memoryarrangement as a whole. Thus, such “virtual machines” appear, function,and/or operate as independent physical machines, though in actualitythey share, or reside on, a single common physical machine. Such anarrangement of “n” “virtual machines” 2D410 is depicted in FIG. 2D.

In FIG. 2D, a single physical machine 2D401 is indicated made up fromhardware 2D402 and a hypervisor and/or operating system 2D403. Shown tobe operating within machine 2D401 and above the hypervisor/operatingsystem layer, are n “virtual machines” 2D410 (that is, 2D410/1, 2D410/2. . . 2D410/n), each with a substantially independent, isolated and/orprotected local memory (typically formed from some subset of the totalmemory of machine 2D401).

Each such “virtual machine” 2D410 for the purposes of this invention mayconstitute a single “replicated memory instance”, which is able tobehave as, and operate as, a “single machine” of a replicated sharedmemory arrangement.

When two or more such “virtual machines” reside on, or operate within, asingle physical machine, then each such single “virtual machine” willtypically represent a single “replicated memory instance” for thepurposes of replicated shared memory arrangements. In otherwords, each“virtual machine” with a memory substantially independent of any other“virtual machine”, when operating as a member of a plurality of“replicated memory instance” in a replicated shared memory arrangement,will typically represent and operate as a single “replicated memoryinstance”, which for the purposes of this invention constitutes a single“machine” in the described embodiments, drawings, arrangements,description, and methods contained herein.

Thus, it is provided by this invention that a replicated shared memoryarrangement, and the methods of this invention applied and operatingwithin such an arrangement, may take the form of a plurality of“replicated memory instances”, which may or may not each correspond to asingle independent physical machine. For example, replicated sharedmemory arrangements are provided where such arrangements take the formof a plurality (such as for example 10) of virtual machine instancesoperating as independent “replicated memory instances”, where eachvirtual machine instance operates within one common, shared, physicalmachine.

Alternatively for example, replicated shared memory arrangements areanticipated where such arrangements take the form of some one or morevirtual machine instances of a single physical machine operating asindependent “replicated memory instances” of such an arrangement, aswell as some one or more single physical machines not operating with twoor more “replicated memory instances”.

Further alternatively arrangements of “virtual machines” are alsoprovided and are to be included within the scope of the presentinvention, including arrangements which reside on, or operate on,multiple physical machines and yet represent a single “replicated memoryinstance” for the purposes of a replicated shared memory arrangement.

Turning now to FIG. 3, a schematic illustration of an allocatedapplication memory of a single machine M1 which is “fragmented” betweenreplicated application memory locations/contents/values andnon-replicated application memory locations/contents/values, is shown.Specifically, FIG. 3 shows a prior art arrangement of the local memory3A/31 of a single machine M1 operating as part of multiple computersystem operating as a replicated shared memory arrangement. Within thelocal memory 3A/31 is an allocated application memory 3A/10.Specifically indicated is the fragmented arrangement of replicatedapplication memory locations/contents/values 3A/11 (indicated as aplurality of single cross hatched boxes of various sizes and capacities)amongst the non-replicated application memory locations/contents/values3A/12 within the allocated application memory 3A/10.

In FIG. 4 a first preferred embodiment of the present invention is shownfor storing replicated application memory locations/contents/values andnon-replicated application memory locations/contents/values in allocatedapplication memory. In FIG. 4 a number, “n”, of application runningcomputers or machines M1, M2, M3 . . . Mn operating as a replicatedshared memory arrangement are provided and, if desired, a server machineX can also be provided. Since the server machine is not essential it isindicated in phantom in FIG. 4. All the machines M1-Mn, and X ifpresent, are interconnected via a communications network such as acommodity communications network 53.

As schematically illustrated in FIG. 4, each of the computers M1, M2 . .. Mn has a local main memory 31,32, . . . 38 which can be, but need notbe, the same size/capacity. Also schematically illustrated in FIG. 4,each of the computers M1, M2, . . . Mn has an allocated applicationmemory 10, 20, . . . 80 which can be, but need not be, the samesize/capacity. Each of the allocated application memories is partitionedinto two regions namely a first replicated memory region 11, 21, 31, . .. 81 which is indicated by single cross hatching in FIG. 4 and a secondnon-replicated memory region 12, 22, . . . 82 which is preferably theremainder of the allocated application memory.

In the first replicated memory region 11, 21, . . . 81, each of theapplication memory locations/contents/values are essentially replicatedon two or more of the machines M1, M2, . . . Mn so that substantiallyall the application memory location(s), content(s), value(s),variable(s), object(s), class(es), field(s), array(s), asset(s) etclocated in the first replicated memory region 11, areduplicated/replicated in one or more of the other first replicatedmemory regions 21, . . . 81. Preferably all memory locations of thefirst replicated memory regions are application memory locations, and/orapplication memory values, and/or application memory contents of theapplication program and/or application program code, and accessible by(for example able to be read from and written to by) the applicationprogram and/or executing application program code.

Alternatively, non-application memory locations and/or non-applicationmemory values and/or non-application memory contents may also reside inthe replicated memory regions 11, 21, . . . 81. For example but notlimited to, such non-application memory locations and/or non-applicationmemory values and/or non-application memory contents may includenon-application “count values” as disclosed in the present applicant'sInternational Patent Application No. PCT/AU2007/001490 claiming priorityfrom Australian Patent Application No. 2006 905 527 entitled “AdvancedContention Detection” and to which U.S. Patent Application No.60/850,711 corresponds. The contents of the last mentioned twospecifications are hereby incorporated into the present specification bycross-reference for all purposes.

Briefly stated, the abovementioned data protocol or message formatincludes both the address of a memory location where a value or contentis to be changed, the new value or content, and a count numberindicative of the position of the new value or content in a sequence ofconsecutively sent new values or content.

Thus a sequence of messages are issued from one or more sources.Typically each source is one computer of a multiple computer system andthe messages are memory updating messages which include a memory addressand a (new or updated) memory content.

Thus each source issues a string or sequence of messages which arearranged in a time sequence of initiation or transmission. The problemarises that the communication network 53 cannot always guarantee thatthe messages will be received in their order of transmission. Thus amessage which is delayed may update a specific memory location with anold or stale content which inadvertently overwrites a fresh or currentcontent.

In order to address this problem each source of messages includes acount value in each message. The count value indicates the position ofeach message in the sequence of messages issuing from that source. Thuseach new message from a source has a count value incremented (preferablyby one) relative to the preceding messages. Thus the message recipientis able to both detect out of order messages, and ignore any messageshaving a count value lower than the last received message from thatsource. Thus earlier sent but later received messages do not cause staledata to overwrite current data.

As explained in the abovementioned cross referenced specifications,later received packets which are later in sequence than earlier receivedpackets overwrite the content or value of the earlier received packetwith the content or value of the later received packet. However, in theevent that delays, latency and the like within the network 53 result ina later received packet being one which is earlier in sequence than anearlier received packet, then the content or value of the earlierreceived packet is not overwritten and the later received packet iseffectively discarded. Each receiving computer is able to determinewhere the latest received packet is in the sequence because of theaccompanying count value. Thus if the later received packet has a countvalue which is greater than the last received packet, then the currentcontent or value is overwritten with the newly received content orvalue. Conversely, if the newly received packet has a count value whichis lower than the existing count value, then the received packet is notused to overwrite the existing value or content. In the event that thecount values of both the existing packet and the received packet areidentical, then a contention is signalled and this can be resolved.

This resolution requires a machine which is about to propagate a newvalue for a memory location, and provided that machine is the samemachine which generated the previous value for the same memory location,then the count value for the newly generated memory is not increased byone (1) but instead is increased by more than one such as by beingincreased by two (2) (or by at least two). A fuller explanation iscontained in the abovementioned cross referenced PCT specification.

Additionally, such non-application memory locations and/ornon-application memory values and/or non-application memory contents mayinclude (but are not limited to) non-application “resolution values” asdisclosed in the last two mentioned specifications 60/850,711.Additionally again, such non-application memory locations and/ornon-application memory values and/or non-application memory contents mayinclude (but are not limited to) non-application “reachabilitytables”/“replication tables” as disclosed in International PatentApplication No. PCT/AU2006/001447 (WO 2007/041762) claiming priorityfrom Australian Patent Application No. 2006 905 582 entitled “ModifiedMachine Architecture with Partial Memory Updating” and filed 10 Oct.2005 (to which U.S. patent application Ser. No. 11/583,958 (60/730,543)corresponds) and in International Patent Application No.PCT/AU2006/001448 (WO 2007/041763) claiming priority from AustralianPatent Application No. 2005 905 581 entitled “Modified MachineArchitecture with Enhanced Memory Clean Up” also filed 10 Oct. 2005,(and to which U.S. patent application Ser. No. 11/583,991 (60/730,408)corresponds). The contents of the two last mentioned PCT specificationsare hereby incorporated into the present specification for all purposes.

When non-application memory locations, and/or non-application memoryvalues, and/or non-application memory contents are stored in thereplicated memory regions 11, 21, . . . 81, preferably suchnon-application memory locations/values/contents are inaccessible by theapplication program (such as for example being unable to be read from orwritten to by the executable code of the application program), oralternatively unaccessed by the application program (such as for examplebeing unread or unwritten to by the executable code of the applicationprogram).

Various memory arrangements and methods for non-application accessiblememory regions (that is, memory regions inaccessible to, or unaccessedby, an application program or application program code) are known in theprior art, such as using virtual memory, virtual memory pages, andmemory management units (MMUs) to create memory spaces or memory regionsor memory locations inaccessible to specific instructions or code (suchas for example application program code). Other arrangements are alsoknown in the prior art, such as through the use of namespaces, softwareor application domains, virtual machines, and segregated memory heaps,and all such memory partitioning, segregation, and/or memory accesscontrol methods and arrangements are included within the scope of thepresent invention.

Preferably, it is the application memory content(s) of the replicatedmemory regions 11,21, . . . , 81 which are replicated, and notnecessarily the physical or logical or functional or allocatedapplication memory structure/arrangement and/or local memorystructure/arrangement by which the replicated application memorycontent(s)/value(s) are stored in the local memories 31, 32, . . . 38,allocated application memories 10,20, . . . 80, or replicated memoryregions 11,21, . . . 81. Specifically, the application memory layout,memory format, memory arrangement, and/or memory structure (includingthe local or virtual memory addresses) of the replicated memorylocations of the first replicated memory region 11, 21, . . . 81 of eachmachine M1, M2, . . . Mn may take any form or format or arrangement orlayout or structure, including potentially different forms or formats orarrangements or layouts or structures for each machine. When differinglayouts (or forms, or formats, or arrangements, or structures) areutilised by replicated memory regions 11,21, . . . 81, preferably thereis associated with corresponding replica memorylocations/contents/values of each machine one or more consistent and/orcommon replica identifiers, or alternatively each machine M1, M2 . . .Mn (or alternatively a machine X) maintains an association between eachlocal replica memory location/content/value, and one or morecorresponding replica memory locations/contents/values of one or more ofthe other machines. In addition, changes made by any machine of one ofthe replicated application memory location(s)/content(s) of its firstreplicated memory region, are communicated via the communicationsnetwork 53 to the other ones of the multiple machines in whichcorresponding replicated memory location(s)/content(s) reside in thefirst replicated memory region(s).

Preferably, the replicated memory regions 11,21, . . . 81 comprise a setof logically, or physically, or functionally contiguous or consecutivememory locations of the allocated application memory. For example, inone preferred embodiment, the replicated memory region 11 of machine M1comprises a plurality of contiguous/consecutive local memory addresses(or virtual memory addresses), such as for example a range of memoryaddresses “17-24”. In an alternative example, the replicated memoryregion 11 of machine M1 may take the form of a plurality of contiguousor consecutive virtual memory pages.

The second non-replicated memory region 12, 22, . . . 82 of each of thelocal memories is independent and not replicated on any other machine,and thus the contents of the second non-replicated memory region arelikely to be substantially dissimilar, and changes made to thecontent/values of a memory location of the second non-replicated memoryregion of any one of the computers M1, M2, . . . Mn are not communicatedto the other computers. Specifically, the memory locations of the secondnon-replicated memory region are not replicated memory locations on atleast two machines of the multiple computer systems comprising machinesM1 . . . Mn. In this connection the disclosure of International PatentApplication No. PCT/AU2006/001447 (WO 2007/041762) claiming priorityfrom Australian Patent Application No. 2006 905 582 entitled “ModifiedMachine Architecture with Partial Memory Updating” and filed 10 Oct.2005 (to which U.S. patent application Ser. No. 11/583,958 (60/730,543)corresponds) and International Patent Application No. PCT/AU2006/001448(WO 2007/041763) claiming priority from Australian Patent ApplicationNo. 2005 905 581 entitled “Modified Machine Architecture with EnhancedMemory Clean Up” also filed 10 Oct. 2005, (and to which U.S. patentapplication Ser. No. 11/583,991 (60/730,408) corresponds) areincorporated herein by cross reference for all purposes.

Briefly those specifications describe a technique whereby either thecomputers M1, M2, . . . Mn, themselves, or the server computer X ifpresent, keep track of the creation, or deletion or placement ofobjects, fields, etc within the individual allocated applicationmemories 10, 20, . . . 80 and determine which of these requirereplication and updating and which do not.

Preferably, the second non-replicated memory regions 12,22, . . . 82 areutilised for the non-replicated application memorylocations/contents/values of each respective machine. Preferably, thenon-replicated application memory locations/contents/values arelogically, or physically, or functionally contiguous or consecutivememory locations/contents/values of the second non-replicated memoryregions 12,22, . . . 82 of the allocated application memory 10,20 . . .80. For example, in one preferred embodiment, the non-replicated memoryregion 12 of machine M1 takes the form of a plurality of contiguous orconsecutive local memory addresses (or virtual memory addresses), suchas for example a range of memory addresses “25-94”. In an alternativeexample, the non-replicated memory region 12 of machine M1 takes theform of a plurality of contiguous or consecutive virtual memory pages.Optionally, the second non-replicated memory regions 12,22, . . . 82takes the form of any remaining allocated application memory which isnot (or does not contain or include) replicated application memorylocations/contents/values, such as for example including “free memory”,“available memory”, “unused memory”, and “allocated but unused” memory.

In relation to the first replicated memory regions 11, 21, . . . 81,from time to time the number of replicated application memory contents,values, objects, fields, arrays etc will increase, thereby resulting ina need for each of the computers M1, M2, . . . Mn (or alternatively,only those computers on which any additionally replicated memorycontents are to be replicated) to allocate more space to the firstreplicated memory region 11, 21, . . . 81 to be used to store theadditionally replicated application memory contents, values, objects,fields, arrays, etc. This is schematically illustrated in FIG. 4 by adouble hatched area which constitutes an additional replicated memoryregion 13, 23, . . . 83. Preferably, the additionally replicated memoryregions 13, 23, . . . 83 are allocated so as to be logically and/orphysically and/or functionally contiguous or consecutive to the previous(first) replicated memory regions 11, 21, . . . 81.

In one preferred embodiment of the present invention, the additionalreplicated regions 13, 23, . . . 83 are allocated (or created, orinitialised, or chosen) as a set of contiguous or consecutive memoryaddresses to the previous (first) replicated memory regions 11, 21, . .. 81 in the allocated application memories 10,20, . . . 80. For example,were the replicated memory region 11 of machine M1 to takes the form ofthe range of local memory addresses “17-24”, then preferably theadditional replicated memory region 13 of machine M1 would be allocated(or created, or initialised, or chosen) as contiguous or consecutivememory addresses of the range of memory addresses to the previous(first) replicated memory region 11—such as for example the range ofmemory addresses “25-31”. In an alternative example, were the replicatedmemory region 11 of machine M1 to take the form of a plurality ofvirtual memory pages, then preferably the additional replicated memoryregion 13 of machine M1 would be allocated as contiguous or consecutivevirtual memory pages to the plurality of contiguous/consecutive virtualmemory pages of the previous (first) replicated memory region 11.Therefore, the allocation and/or storing (or creating, or initialising,or choosing) of additional replicated memory regions to be contiguous orconsecutive with a previously replicated memory region, may beconsidered to logically, physically, or functionally expand the previousreplicated memory region, and together the previous replicated memoryregion and the additional replicated memory region preferably take theform of a single contiguous or consecutive replicated memory region.

In an embodiment where the size of each of the allocated applicationmemories 10, 20, . . . 80 remains constant (or is to remain constant),then growth of the first replicated memory regions 11, 21, . . . 81(such as by the addition of the additional replicated memory regions13,23, . . . 83) will cause the second non-replicated memory regions 12,22, . . . 82 to shrink to a corresponding extent. In such an embodimentas described above, preferably any “free memory”, or “unused memory”, or“available” memory, or “allocated but unused” memory of the secondmemory region which is contiguous or consecutive to the previous (first)replicated memory region is preferably used for such additionalreplicated memory region. Alternatively, “occupied memory”, “usedmemory”, “unavailable memory”, or other “allocated and used” memory ofthe second non-replicated memory region which is logically, orphysically, or functionally contiguous or consecutive to the previous(first) replicated memory region, may be moved or relocated or copied toa different position/location/place within the second non-replicatedmemory region, so as to make available the previously occupied (or usedor unavailable) contiguous or consecutive memory of the secondnon-replicated memory region for the additional replicated memoryregion(s).

Additionally, non-commercial operation of a prototype multiple computersystem operating as a replicated shared memory arrangement has revealedthat typically an increase in the amount of replicated memory of anapplication program operating in a replicated shared memory arrangementcorresponds to a reduction (either of the same amount, or a lesseramount) in the amount of non-replicated application memory utilised.Therefore, the abovedescribed allocation (or creation, orinitialisation, or choosing) method is advantageous for applicationprograms which exhibit such abovementioned characteristics.Additionally, such an allocation (or creation, or initialisation)arrangement as described above is therefore advantageous where allocatedapplication memory 10,20, . . . 80 remains constant (or is to remainconstant).

However, in an alternative embodiment of the present invention, it isalso possible to adjust the size of the local application memories 10,20, . . . 80 so that if, for example, the first replicated memoryregions 11, 21, . . . 81 grow in size, this growth is accommodated bygrowth of the local application memories 10,20, . . . 80, and the sizeof the second memory regions 12, 22, . . . 82 remain unaltered. Whensuch an alternative arrangement as this is employed, and additionalapplication memory is to be allocated for the additional replicatedmemory 13,23, . . . 83, preferably such additionally allocated (orcreated, or initialised, or chosen) application memory is contiguous orconsecutive to the first (previous) replicated memory region 11,21, . .. 81. For example, in one preferred embodiment, the additionallyallocated application memory to be used for the additional replicatedmemory region 13 of machine M1 comprises a plurality of contiguous orconsecutive local memory addresses (or virtual memory addresses), suchas for example a range of memory addresses “10-16”, which are contiguousor consecutive to the local memory addresses of the previous (first)replicated memory region 11 of machine M1 (e.g. the range of memoryaddresses “17-24”). In an alternative example, the additionallyallocated application memory to be used for the additional replicatedmemory region 13 of machine M1 take the form of a plurality ofcontiguous or consecutive virtual memory pages. Other local memory sizeadjustments and control schemes can additionally, or alternatively, beapplied.

Regardless of from where the local memory to be used as the additionalreplicated memory regions 13,23, . . . 83 is sourced (that is, whethersuch memory is additionally allocated application memory, or whethersuch memory was previously part of the second non-replicated memoryregion), the additional replicated memory regions 13, 23, . . . 83 arelogically, or physically, or functionally contiguous or consecutive tothe previous (first) replicated memory regions 11, 21, . . . 81.Together, the additional replicated memory regions 13,23, . . . 83, andthe previous (first) replicated memory region 11,21, . . . 81, take theform of or constitute the replicated application memory contents/values,which are preferably stored and/or arranged in a contiguous orconsecutive manner (or form, or format, or layout). Thus, fragmentationbetween replicated application memory locations/contents/values andnon-replicated application memory locations/contents/values of allocatedapplication memory is reduced, and efficient operation of the allocatedapplication memories is achieved.

It follows from the above that the abovedescribed arrangement reducesthe likelihood of fragmentation of the allocated application memoryoccurring between the replicated memory locations/contents andnon-replicated application memory locations/contents therein.

Preferably there is a single replicated memory region 11,21, . . . 81 ofmachines M1,M2 . . . Mn, however more than one replicated memory regionper allocated application memory is provided or may be required—such asfor example, two replicated memory regions which are non-contiguous ornon-consecutive with each other. Specifically, it may not always bepossible to allocate or store all replicated application memorylocations/contents/values in a single contiguous or consecutive memoryregion (such as the single replicated memory regions 11,21, . . . 81).However, when such is the case, the above methods still apply, where“uncontrolled” fragmentation between replicated application memorylocations/contents/values and non-replicated application memorylocations/contents/values is sought to be minimised, reduced, or avoidedaltogether.

When more than one replicated memory region 11,21, . . . 81 exists inallocated application memory, preferably such multiple replicated memoryregions take the form of regions of contiguous or consecutive memorylocations and/or addresses etc. When multiple replicated memory regionsexist within an allocated application memory 10, 20, . . . 80,preferably any additional replicated memory regions (such as theadditional replicated memory region 13, 23, . . . 83) are allocated orstored contiguously to, or consecutively to, at least one of theprevious replicated memory regions. Consequently, in doing so the numberof independent replicated memory regions and/or independent replicatedmemory locations is kept to the minimum possible in number, by alwaysseeking to allocate or store (or create, or initialise, or chose)additional replicated application memory location/contents/values so asto be contiguous or consecutive to at least one of the previousreplicated memory regions.

It is even possible as indicated in FIG. 5 for the first parts 11, 21, .. . 81 to constitute substantially all of the individual local memories10, 20, . . . 80 as indicated in FIG. 5. This situation is furtherdescribed in the abovementioned patent applications.

Each of the individual computers M1, M2, . . . Mn can be a differentcomputer manufactured by a different manufacturer and having, forexample, a different operating system, a different processor, etc andthis is schematically indicated in FIGS. 3-5 by the arrangement of eachof the local memories 10, 20, . . . 80 being different. For example,different computers can have different memory formats (such as BigEndian and Little Endian conventions, for example). Additionally, oralternatively, the way in which the allocated application memory ispartitioned can also be different for each machine (as schematicallyillustrated in FIGS. 3-5).

Practical experience on a non-commercial prototype multiple computersystem indicates that the volume of the replicated memory region 11, 21,. . . 81 (and including any additionally allocated contiguous replicatedmemory regions, such as additionally replicated memory region 13,23, . .. 83) is typically less than approximately half the corresponding localmemory 10, 20, . . . 80 and usually within the range of approximately 5%to approximately 40% of the local memory. Typically, the replicatedmemory regions 11, 21, . . . 81 occupies from 10% to 30% of the localmemory. The below examples indicate some test results for particularembodiments of the invention but are not limitations on the invention.

If, for ease of exemplification, each total local memory 10, 20, . . .80 is assumed to be 100 Megabytes, then in an idealised distributedshared memory arrangement, the total memory available to the multiplecomputer system assuming eight machines would be 800 Megabytes.Conversely, in an idealised replicated shared memory system the totalmemory available would be only 100 Megabytes. However, in the hybridreplicated shared memory system as described in FIG. 3B, if the memoryallocated to the first part 11, 21, . . . 81 is 10% or 10 Megabytes andthus the memory allocated to the second part 12, 22, . . . 82 is 90Megabytes, then the total memory available to the system is the sum ofthe memory allocated to the first part (10 Megabytes) plus the number ofmachines in the multiple computer system times the memory allocated tothe second part, or 10+(8×90) Megabytes=730 Megabytes. This represents730/800 or 91.25% of the idealised distributed shared memory.Conversely, if under the same arrangements the percentage of localmemory allocated to the first part 11, 21, . . . 81 rises to 30% andthus occupies 30 Megabytes, then the total memory available to themultiple computer system is 30+(8×70) Megabytes=590 Megabytes or 590/800or 73.75% of the idealised distributed shared memory.

It follows from the above that the abovedescribed arrangement enables anappreciable percentage of the idealised distribution shared memory to beavailable to a multiple computer system as a result of the hybridreplicated shared memory arrangement described herein.

It is to be understood that the independent local memory 10, 20, . . .80 of each machine represents only that of the machine's total memorywhich is allocated to that portion of the application program running onthat machine. Thus other memory will be occupied by the machine'soperating system and other computational tasks unrelated to theapplication program.

The foregoing describes only some embodiments of the present inventionand modifications, obvious to those skilled in the art, can be madethereto without departing from the scope of the present invention. Forexample, reference to JAVA includes both the JAVA language and also JAVAplatform and architecture.

In all described instances of modification, where the application code50 is modified before, or during loading, or even after loading butbefore execution of the unmodified application code has commenced, it isto be understood that the modified application code is loaded in placeof, and executed in place of, the unmodified application codesubsequently to the modifications being performed.

The term “distributed runtime system”, “distributed runtime”, or “DRT”and such similar terms used herein are intended to capture or includewithin their scope any application support system (potentially ofhardware, or firmware, or software, or combination and potentiallycomprising code, or data, or operations or combination) to facilitate,enable, and/or otherwise support the operation of an application programwritten for a single machine (e.g. written for a single logicalshared-memory machine) to instead operate on a multiple computer systemwith independent local memories and operating in a replicated sharedmemory arrangement. Such DRT or other “application support software” maytake many forms, including being either partially or completelyimplemented in hardware, firmware, software, or various combinationstherein.

The methods of this invention described herein are preferablyimplemented in such an application support system, such as DRT describedin International Patent Application No. PCT/AU2005/000580 publishedunder WO 2005/103926 (and to which U.S. patent application Ser. No.111/111,946 corresponds), however this is not a requirement of thisinvention. Alternatively, an implementation of the methods of thisinvention may comprise a functional or effective application supportsystem (such as a DRT described in the abovementioned PCT specification)either in isolation, or in combination with other softwares, hardwares,firmwares, or other methods of any of the above incorporatedspecifications, or combinations therein.

The reader is directed to the abovementioned PCT specification for afull description, explanation and examples of a distributed runtimesystem (DRT) generally, and more specifically a distributed runtimesystem for the modification of application program code suitable foroperation on a multiple computer system with independent local memoriesfunctioning as a replicated shared memory arrangement, and thesubsequent operation of such modified application program code on suchmultiple computer system with independent local memories operating as areplicated shared memory arrangement.

Also, the reader is directed to the abovementioned PCT specification forfurther explanation, examples, and description of various anticipatedmethods and means which may be used to modify application program codeduring loading or at other times.

Also, the reader is directed to the abovementioned PCT specification forfurther explanation, examples, and description of various methods andmeans which may be used to modify application program code suitable foroperation on a multiple computer system with independent local memoriesand operating as a replicated shared memory arrangement.

Finally, the reader is directed to the abovementioned PCT specificationfor further explanation, examples, and description of various methodsand means which may be used to operate replicated memories of areplicated shared memory arrangement, such as updating of replicatedmemories when one of such replicated memories is written-to or modified.

The term “array”, “array data structure”, “array data type” and suchsimilar terms used herein are intended to capture or include withintheir scope any set of memory locations, where such set is preferably alogically related or contiguous or consecutive or neighbouring set ofmemory locations. Importantly, such logically related or contiguousmemory locations are not required to in actuality be contiguous orconsecutive or neighbouring memory locations within the local memory ofa machine (such as for example occupying physically contiguous,neighbouring, consecutive or related bits or bytes of a memory circuitor memory chip), but instead that for the purposes of the operation of aloop structure or other loop code-sequence of an application programcode, the set of memory locations appear functionally and/or logicallycontiguous and/or consecutive and/or neighbouring and/or related memorylocations.

In alternative multicomputer arrangements, such as distributed sharedmemory arrangements and more general distributed computing arrangements,the above described methods may still be applicable, advantageous, andused. Specifically, any multi-computer arrangement where replica,“replica-like”, duplicate, mirror, cached or copied memory locationsexist, such as any multiple computer arrangement where memory locations(singular or plural), objects, classes, libraries, packages etc areresident on a plurality of connected machines and preferably updated toremain consistent, then the methods are applicable. For example,distributed computing arrangements of a plurality of machines (such asdistributed shared memory arrangements) with cached memory locationsresident on two or more machines and optionally updated to remainconsistent comprise a functional “replicated memory system” with regardto such cached memory locations, and is to be included within the scopeof the present invention. Thus, it is to be understood that theaforementioned methods apply to such alternative multiple computerarrangements. The above disclosed methods may be applied in such“functional replicated memory systems” (such as distributed sharedmemory systems with caches) mutatis mutandis.

It is also provided and envisaged that any of the described functions oroperations described as being performed by an optional server machine X(or multiple optional server machines) may instead be performed by anyone or more than one of the other participating machines of theplurality (such as machines M1, M2, M3 . . . Mn of FIG. 2A or 2B).

Alternatively or in combination, it is also further provided andenvisaged that any of the described functions or operations described asbeing performed by an optional server machine X (or multiple optionalserver machines) may instead be partially performed by (for examplebroken up amongst) any one or more of the other participating machinesof the plurality, such that the plurality of machines taken togetheraccomplish the described functions or operations described as beingperformed by an optional machine X. For example, the described functionsor operations described as being performed by an optional server machineX may broken up amongst one or more of the participating machines of theplurality.

Further alternatively or in combination, it is also further provided andenvisaged that any of the described functions or operations described asbeing performed by an optional server machine X (or multiple optionalserver machines) may instead be performed or accomplished by acombination of an optional server machine X (or multiple optional servermachines) and any one or more of the other participating machines of theplurality (such as machines M1, M2, M3 . . . Mn), such that theplurality of machines and optional server machines taken togetheraccomplish the described functions or operations described as beingperformed by an optional single machine X. For example, the describedfunctions or operations described as being performed by an optionalserver machine X may broken up amongst one or more of an optional servermachine X and one or more of the participating machines of theplurality.

The terms “object” and “class” used herein are derived from the JAVAenvironment and are intended to embrace similar terms derived fromdifferent environments, such as modules, components, packages, structs,libraries, and the like.

The use of the term “object” and “class” used herein is intended toembrace any association of one or more memory locations. Specificallyfor example, the term “object” and “class” is intended to include withinits scope any association of plural memory locations, such as a relatedset of memory locations (such as, one or more memory locationscomprising an array data structure, one or more memory locationscomprising a struct, one or more memory locations comprising a relatedset of variables, or the like).

Reference to JAVA in the above description and drawings includes,together or independently, the JAVA language, the JAVA platform, theJAVA architecture, and the JAVA virtual machine. Additionally, thepresent invention is equally applicable mutatis mutandis to othernon-JAVA computer languages (including for example, but not limited toany one or more of, programming languages, source-code languages,intermediate-code languages, object-code languages, machine-codelanguages, assembly-code languages, or any other code languages),machines (including for example, but not limited to any one or more of,virtual machines, abstract machines, real machines, and the like),computer architectures (including for example, but not limited to anyone or more of, real computer/machine architectures, or virtualcomputer/machine architectures, or abstract computer/machinearchitectures, or microarchitectures, or instruction set architectures,or the like), or platforms (including for example, but not limited toany one or more of, computer/computing platforms, or operating systems,or programming languages, or runtime libraries, or the like).

Examples of such programming languages include procedural programminglanguages, or declarative programming languages, or object-orientedprogramming languages. Further examples of such programming languagesinclude the Microsoft.NET language(s) (such as Visual BASIC, VisualBASIC.NET, Visual C/C++, Visual C/C++.NET, C#, C#.NET, etc), FORTRAN,C/C++, Objective C, COBOL, BASIC, Ruby, Python, etc.

Examples of such machines include the JAVA Virtual Machine, theMicrosoft.NET CLR, virtual machine monitors, hypervisors, VMWare, Xen,and the like.

Examples of such computer architectures include, Intel Corporation's x86computer architecture and instruction set architecture, IntelCorporation's NetBurst microarchitecture, Intel Corporation's Coremicroarchitecture, Sun Microsystems' SPARC computer architecture andinstruction set architecture, Sun Microsystems' UltraSPARC IIImicroarchitecture, IBM Corporation's POWER computer architecture andinstruction set architecture, IBM Corporation's POWER4/POWER5/POWER6microarchitecture, and the like.

Examples of such platforms include, Microsoft's Windows XP operatingsystem and software platform, Microsoft's Windows Vista operating systemand software platform, the Linux operating system and software platform,Sun Microsystems' Solaris operating system and software platform, IBMCorporation's AIX operating system and software platform, SunMicrosystems' JAVA platform, Microsoft's.NET platform, and the like.

When implemented in a non-JAVA language or application code environment,the generalized platform, and/or virtual machine and/or machine and/orruntime system is able to operate application code 50 in the language(s)(including for example, but not limited to any one or more ofsource-code languages, intermediate-code languages, object-codelanguages, machine-code languages, and any other code languages) of thatplatform, and/or virtual machine and/or machine and/or runtime systemenvironment, and utilize the platform, and/or virtual machine and/ormachine and/or runtime system and/or language architecture irrespectiveof the machine manufacturer and the internal details of the machine. Itwill also be appreciated in light of the description provided hereinthat platform and/or runtime system may include virtual machine andnon-virtual machine software and/or firmware architectures, as well ashardware and direct hardware coded applications and implementations.

For a more general set of virtual machine or abstract machineenvironments, and for current and future computers and/or computingmachines and/or information appliances or processing systems, and thatmay not utilize or require utilization of either classes and/or objects,the structure, method, and computer program and computer program productare still applicable. Examples of computers and/or computing machinesthat do not utilize either classes and/or objects include for example,the x86 computer architecture manufactured by Intel Corporation andothers, the SPARC computer architecture manufactured by SunMicrosystems, Inc and others, the PowerPC computer architecturemanufactured by International Business Machines Corporation and others,and the personal computer products made by Apple Computer, Inc., andothers. For these types of computers, computing machines, informationappliances, and the virtual machine or virtual computing environmentsimplemented thereon that do not utilize the idea of classes or objects,may be generalized for example to include primitive data types (such asinteger data types, floating point data types, long data types, doubledata types, string data types, character data types and Boolean datatypes), structured data types (such as arrays and records) derivedtypes, or other code or data structures of procedural languages or otherlanguages and environments such as functions, pointers, components,modules, structures, references and unions.

In the JAVA language memory locations include, for example, both fieldsand elements of array data structures. The above description deals withfields and the changes required for array data structures areessentially the same mutatis mutandis.

Any and all embodiments of the present invention able to take numerousforms and implementations, including in software implementations,hardware implementations, silicon implementations, firmwareimplementation, or software/hardware/silicon/firmware combinationimplementations.

Various methods and/or means are described relative to embodiments ofthe present invention. In at least one embodiment of the invention, anyone or each of these various means may be implemented by computerprogram code statements or instructions (including by a plurality ofcomputer program code statements or instructions) that execute withincomputer logic circuits, processors, ASICs, microprocessors,microcontrollers, or other logic to modify the operation of such logicor circuits to accomplish the recited operation or function. In anotherembodiment, any one or each of these various means may be implemented infirmware and in other embodiments such may be implemented in hardware.Furthermore, in at least one embodiment of the invention, any one oreach of these various means may be implemented by a combination ofcomputer program software, firmware, and/or hardware.

Any and each of the aforedescribed methods, procedures, and/or routinesmay advantageously be implemented as a computer program and/or computerprogram product stored on any tangible media or existing in electronic,signal, or digital form. Such computer program or computer programproducts having instructions separately and/or organized as modules,programs, subroutines, or in any other way for execution in processinglogic such as in a processor or microprocessor of a computer, computingmachine, or information appliance; the computer program or computerprogram products modifying the operation of the computer on which itexecutes or on a computer coupled with, connected to, or otherwise insignal communications with the computer on which the computer program orcomputer program product is present or executing. Such computer programor computer program product modifying the operation and architecturalstructure of the computer, computing machine, and/or informationappliance to alter the technical operation of the computer and realizethe technical effects described herein.

For ease of description, some or all of the indicated memory locationsherein may be indicated or described to be replicated on each machine(as shown in FIG. 2A), and therefore, replica memory updates to any ofthe replicated memory locations by one machine, will be transmitted/sentto all other machines. Importantly, the methods and embodiments of thisinvention are not restricted to wholly replicated memory arrangements,but are applicable to and operable for partially replicated sharedmemory arrangements mutatis mutandis (e.g. where one or more memorylocations are only replicated on a subset of a plurality of machines,such as shown in FIG. 2B).

Any combination of any of the described methods or arrangements hereinare provided and envisaged, and to be included within the scope of thepresent invention.

Alternatively, in the instances where modification takes place afterloading and after execution of the unmodified application code hascommenced, it is to be understood that the unmodified application codemay either be replaced with the modified application code in whole,corresponding to the modifications being performed, or alternatively,the unmodified application code may be replaced in part or incrementallyas the modifications are performed incrementally on the executingunmodified application code. Regardless of which such modificationroutes are used, the modifications subsequent to being performed executein place of the unmodified application code.

It is advantageous to use a global identifier is as a form of‘meta-name’ or ‘meta-identity’ for all the similar equivalent localobjects (or classes, or assets or resources or the like) on each one ofthe plurality of machines M1, M2 . . . Mn. For example, rather thanhaving to keep track of each unique local name or identity of eachsimilar equivalent local object on each machine of the plurality ofsimilar equivalent objects, one may instead define or use a global namecorresponding to the plurality of similar equivalent objects on eachmachine (e.g. “globalname7787”), and with the understanding that eachmachine relates the global name to a specific local name or object (e.g.“globalname7787” corresponds to object “localobject456” on machine M1,and “globalname7787” corresponds to object “localobject885” on machineM2, and “globalname7787” corresponds to object “localobject111” onmachine M3, and so forth).

It will also be apparent to those skilled in the art in light of thedetailed description provided herein that in a table or list or otherdata structure created by each DRT 71 when initially recording orcreating the list of all, or some subset of all objects (e.g. memorylocations or fields), for each such recorded object on each machine M1,M2 . . . Mn there is a name or identity which is common or similar oneach of the machines M1, M2 . . . Mn. However, in the individualmachines the local object corresponding to a given name or identity willor may vary over time since each machine may, and generally will, storememory values or contents at different memory locations according to itsown internal processes. Thus the table, or list, or other data structurein each of the DRTs will have, in general, different local memorylocations corresponding to a single memory name or identity, but eachglobal “memory name” or identity will have the same “memory value orcontent” stored in the different local memory locations. So for eachglobal name there will be a family of corresponding independent localmemory locations with one family member in each of the computers.Although the local memory name may differ, the asset, object, locationetc has essentially the same content or value. So the family iscoherent.

The term “table” or “tabulation” as used herein is intended to embraceany list or organised data structure of whatever format and within whichdata can be stored and read out in an ordered fashion.

It will also be apparent to those skilled in the art in light of thedescription provided herein that the abovementioned modification of theapplication program code 50 during loading can be accomplished in manyways or by a variety of means. These ways or means include, but are notlimited to at least the following five ways and variations orcombinations of these five, including by:

-   -   (i) re-compilation at loading,    -   (ii) a pre-compilation procedure prior to loading,    -   (iii) compilation prior to loading,    -   (iv) “just-in-time” compilation(s), or    -   (v) re-compilation after loading (but, for example, before        execution of the relevant or corresponding application code in a        distributed environment).

Traditionally the term “compilation” implies a change in code orlanguage, for example, from source to object code or one language toanother. Clearly the use of the term “compilation” (and its grammaticalequivalents) in the present specification is not so restricted and canalso include or embrace modifications within the same code or language.

Those skilled in the computer and/or programming arts will be aware thatwhen additional code or instructions is/are inserted into an existingcode or instruction set to modify same, the existing code or instructionset may well require further modification (such as for example, byre-numbering of sequential instructions) so that offsets, branching,attributes, mark up and the like are properly handled or catered for.

Similarly, in the JAVA language memory locations include, for example,both fields and array types. The above description deals with fields andthe changes required for array types are essentially the same mutatismutandis. Also the present invention is equally applicable to similarprogramming languages (including procedural, declarative and objectorientated languages) to JAVA including Microsoft.NET platform andarchitecture (Visual Basic, Visual C/C++, and C#) FORTRAN, C/C++, COBOL,BASIC etc.

The terms object and class used herein are derived from the JAVAenvironment and are intended to embrace similar terms derived fromdifferent environments such as dynamically linked libraries (DLL), orobject code packages, or function unit or memory locations.

The above arrangements may be implemented by computer program codestatements or instructions (including by a plurality of computer programcode statements or instructions) that execute within computer logiccircuits, processors, ASICs, logic or electronic circuit hardware,microprocessors, microcontrollers or other logic to modify the operationof such logic or circuits to accomplish the recited operation orfunction. In another arrangement the implementation may be in firmwareand in other arrangements may be in hardware. Furthermore, any one oreach of these implementations may be a combination of computer programsoftware, firmware, and/or hardware.

Any and each of the abovedescribed methods, procedures, and/or routinesmay advantageously be implemented as a computer program and/or computerprogram product stored on any tangible media or existing in electronic,signal, or digital form. Such computer program or computer programproducts comprising instructions separately and/or organized as modules,programs, subroutines, or in any other way for execution in processinglogic such as in a processor or microprocessor of a computer, computingmachine, or information appliance; the computer program or computerprogram products modifying the operation of the computer in which itexecutes or on a computer coupled with, connected to, or otherwise insignal communications with the computer on which the computer program orcomputer program product is present or executing. Such a computerprogram or computer program product modifies the operation andarchitectural structure of the computer, computing machine, and/orinformation appliance to alter the technical operation of the computerand realize the technical effects described herein.

The invention may therefore be constituted by a computer program productcomprising a set of program instructions stored in a storage medium orexisting electronically in any form and operable to permit a pluralityof computers to carry out any of the methods, procedures, routines, orthe like as described herein including in any of the claims.

Furthermore, the invention includes (but is not limited to) a pluralityof computers, or a single computer adapted to interact with a pluralityof computers, interconnected via a communication network or othercommunications link or path and each operable to substantiallysimultaneously or concurrently execute the same or a different portionof an application code written to operate on only a single computer on acorresponding different one of computers. The computers are programmedto carry out any of the methods, procedures, or routines described inthe specification or set forth in any of the claims, on being loadedwith a computer program product or upon subsequent instruction.Similarly, the invention also includes within its scope a singlecomputer arranged to co-operate with like, or substantially similar,computers to form a multiple computer system.

To summarize, there is disclosed a multiple computer system withreplicated shared memory, the system comprising a multiplicity ofcomputers each interconnected via a communications network and eachexecuting a different portion of an applications program written to beexecuted on only a single computer, wherein each the computer has anindependent local memory partitioned into two regions, a first one ofthe regions being substantially similar with corresponding memorycontent replicated on at least one other computer and the second of theregions not corresponding to each other.

Preferably changes to the content of replicated memory in the firstregion of the local memory of any one of the multiple computers aretransmitted via the communications network to the correspondingreplicated memory in the first region of all the other ones of themultiple computers.

Preferably additions and/or deletions to the memory locations in thefirst region of the local memory of any one of the multiple computersare transmitted via the communications network to the first region ofall the other ones of the multiple computers whereby the partitionbetween the first and second regions changes with time.

Preferably the first region occupies less than substantially 50% of thelocal memory of each the multiple computer.

Preferably the first region occupies from substantially 5% tosubstantially 40% of the local memory of each the computer.

Preferably the first region occupies from substantially 10% tosubstantially 30% of the local memory of each the computer.

Also disclosed is a method of partitioning an independent local memoryof each computer of a multiple computer system comprising a multiplicityof computers each interconnected via a communications system and eachexecuting a different portion of an applications program written to beexecuted on only a single computer, the method comprising the step of:

(i) for each the computer partitioning the independent local memory intotwo regions, a first one of the regions being substantially similar withcorresponding memory content replicated on at least one other computer,and the second of the regions not corresponding to each other.

Preferably the method includes the further step of:

(ii) transmitting via the communications network changes to thereplicated content of memory in the first region of the local memory ofany one of the multiple computers to the corresponding replicated memoryof all the other ones of the multiple computers.

Preferably the method includes the further step of:

(iii) changing the partition between the first and second region withtime by transmitting via the communications network additions and/ordeletions to the memory locations in the first region of the localmemory of any one of the multiple computers to the first region of allthe other ones of the multiple computers.

Preferably the method includes the further step of:

(iv) allocating less than substantially 50% of the local memory of eachthe multiple computer to the first region.

Preferably the method includes the step of:

(v) allocating from substantially 5% to substantially 40% of the localmemory to the first region.

Preferably the method includes the step of:

(vi) allocating from substantially 10% to substantially 30% of the localmemory to the first region.

In addition there is disclosed a single computer for operation incooperation with an external multiple computer system with replicatedshared memory, the system comprising a multiplicity of single computerseach interconnected via a communications network and each executing adifferent portion of an applications program written to be executed ononly a single computer, wherein each the single computer has anindependent local memory partitioned into two regions, a first one ofthe regions being substantially similar with corresponding memorycontent replicated on at least one other computer, and the second of theregions not corresponding to each other.

Preferably changes to the replicated content of the memory in the firstregion of the independent local memory of the single computer aretransmitted via the communications network to the corresponding memoryof all the other ones of the single computers in the multiple computersystem.

Preferably changes to the number of memory locations in the first regionof the independent local memory of the single computer are transmittedvia the communications network to the first region of all the other onesof the single computers of the multiple computer system, whereby thepartition between the first and second regions changes with time.

Preferably the first region occupies less than substantially 50% of thelocal memory of each the single computer.

Preferably the first region occupies from substantially 5% tosubstantially 40% of the independent local memory.

Preferably the first region occupies from substantially 10% tosubstantially 30% of the local memory.

Furthermore, there is disclosed a method of partitioning local memory ofa single computer operating in cooperation with a multiple computersystem comprising a multiplicity of computers each interconnected via acommunications network and each executing a different portion of anapplications program written to be executed on only a single computer,the method comprising the step of:

(i) partitioning the local memory of the single computer in two regions,a first one of the regions being substantially similar withcorresponding memory content replicated on at least one other of thecomputers in the multiple computer system, and the second of the regionsnot corresponding to each other.

Preferably the method includes the further step of:

(ii) transmitting via the communications network changes to the contentof memory in the first region of the local memory of the single computerto the corresponding memory of all the other ones of the computers.

Preferably the method includes the further step of:

(iii) changing the partition between the first and second regions withtime by transmitting via the communications network changes to thenumber of memory locations in the first region of the local memory ofthe single computer to the first region of all the other ones of thecomputers in the multiple computer system.

Preferably the method includes the further step of:

(iv) allocating less than substantially 50% of the local memory of eachthe computer to the first region.

Preferably the method includes the further step of:

(v) allocating from substantially 5% to substantially 40% of theindependent local memory to the first region.

Preferably the method includes the further step of:

(vi) allocating from substantially 10% to substantially 50% of theindependent local memory to the first region.

In addition there is disclosed a multiple computer system withreplicated shared memory, the system comprising a multiplicity ofcomputers each interconnected via a communications network and eachexecuting a different portion of an applications program written to beexecuted on only a single computer, wherein each the computer has anindependent local memory partitioned into an allocated applicationmemory, the allocated application memory being further partitioned intotwo regions, a first one of the regions comprising application memorycontents replicated in at least one other of the computers, and thesecond of the regions comprising application memory contents notreplicated in any other of the computers.

Preferably changes to the replicated content of memory in the firstregion of the allocated application memory of any one of the multiplecomputers are transmitted via the communications network to thecorresponding replicated memory in the first region of at least oneother of the multiple computers.

Preferably additions and/or deletions to the memory locations in thefirst region of the allocated application memory of any one of themultiple computers are transmitted via the communications network to thefirst region of at least one other of the multiple computers whereby thepartition between the first and second regions changes with time.

Preferably the first region occupies less than substantially 50% of theallocated application memory of each the multiple computer.

Preferably the first region occupies from substantially 5% tosubstantially 40% of the allocated application memory of each thecomputer.

Preferably the first region occupies from substantially 10% tosubstantially 30% of the allocated application memory of each thecomputer.

Still further there is disclosed a method of partitioning an independentlocal memory of each computer of a multiple computer system comprising amultiplicity of computers each interconnected via a communicationssystem and each executing a different portion of an applications programwritten to be executed on only a single computer, the method comprisingthe step of:

(i) for each the computer partitioning the independent local memory intoan allocated application memory, the allocated application memory beingfurther partitioned into two regions, a first one of the regionscomprising application memory contents replicated in at least on otherof the computers, and the second of the regions comprising applicationmemory contents not replicated in any other of the computers.

Preferably the method includes the further step of:

(ii) transmitting via the communications network changes to thereplicated content of memory in the first region of the allocatedapplication memory of any one of the multiple computers to thecorresponding replicated memory of at least one other of the multiplecomputers.

Preferably the method includes the further step of:

(iii) changing the partition between the first and second region withtime by transmitting via the communications network additions and/ordeletions to the memory locations in the first region of the allocatedapplication memory of any one of the multiple computers to the firstregion of at least one other of the multiple computers.

Preferably the method includes the further step of:

(iv) allocating less than substantially 50% of the allocated applicationmemory of each the multiple computer to the first region.

Preferably the method includes the step of:

(v) allocating from substantially 5% to substantially 40% of theallocated application memory to the first region.

Preferably the method includes the step of:

(vi) allocating from substantially 10% to substantially 30% of theallocated application memory to the first region.

Further still there is disclosed a single computer for operation incooperation with an external multiple computer system with replicatedshared memory, the system comprising a multiplicity of single computerseach interconnected via a communications network and each executing adifferent portion of an applications program written to be executed ononly a single computer, wherein each the single computer has anindependent local memory partitioned into an allocated applicationmemory, the allocated application memory further partitioned into tworegions, a first one of the regions comprising application memorycontents replicated in at least one other of the computers, and thesecond of the regions comprising application memory contents notreplicated in any other of the computers.

Preferably changes to the replicated content of the memory in the firstregion of the allocated application memory of the single computer aretransmitted via the communications network to the corresponding memoryof at least one other of the single computers in the multiple computersystem.

Preferably changes to the number of memory locations in the first regionof the allocated application memory of the single computer aretransmitted via the communications network to the first region of atleast one other of the single computers of the multiple computer system,whereby the partition between the first and second regions changes withtime.

Preferably the first region occupies less than substantially 50% of theallocated application memory of each the single computer.

Preferably the first region occupies from substantially 5% tosubstantially 40% of the allocated application memory.

Preferably the first region occupies from substantially 10% tosubstantially 30% of the allocated application memory.

Also disclosed is a method of partitioning local memory of a singlecomputer operating in cooperation with a multiple computer systemcomprising a multiplicity of computers each interconnected via acommunications network and each executing a different portion of anapplications program written to be executed on only a single computer,the method comprising the step of:

(i) partitioning the local memory of the single computer into anallocated application memory, the allocated application memory furtherpartitioned into two regions, a first one of the regions comprisingapplication memory contents replicated in at least one other of thecomputers in the multiple computer system, and the second of the regionscomprising application memory contents not replicated in any other ofthe computers in the multiple computers system.

Preferably the method includes the further step of:

(ii) transmitting via the communications network changes to the contentof memory in the first region of the allocated application memory of thesingle computer to the corresponding memory of all the other ones of thecomputers.

Preferably the method includes the further step of:

(iii) changing the partition between the first and second regions withtime by transmitting via the communications network changes to thenumber of memory locations in the first region of the allocatedapplication memory of the single computer to the first region of all theother ones of the computers in the multiple computer system.

Preferably the method includes the further step of:

(iv) allocating less than substantially 50% of the allocated applicationmemory of each the computer to the first region.

Preferably the method includes the further step of:

(v) allocating from substantially 5% to substantially 40% of theallocated application memory to the first region.

Preferably the method includes the further step of:

(vi) allocating from substantially 10% to substantially 50% of theallocated application memory to the first region.

The term “comprising” (and its grammatical variations) as used herein isused in the inclusive sense of “having” or “including” and not in theexclusive sense of “consisting only of”.

1. A multiple computer system with replicated shared memory, said systemcomprising: a multiplicity of computers each interconnected via acommunications network and each executing a different portion of anapplications program written to be executed on only a single computer,wherein each said computer has an independent local memory partitionedinto two regions, a first one of said regions having contentcorresponding to corresponding memory content replicated on at least oneother computer, and the second of said regions not corresponding to eachother, wherein changes to the content of replicated memory in the firstregion of the local memory of any one of said multiple computers aretransmitted via said communications network to the correspondingreplicated memory in the first region of all the other ones of saidmultiple computers, wherein additions and/or deletions to the memorylocations in the first region of the local memory of any one of saidmultiple computers are transmitted via said communications network tothe first region of all the other ones of said multiple computerswhereby the partition between said first and second regions changes withtime.
 2. The system of claim 1, wherein said first region occupies lessthan substantially 50% of the local memory of each said multiplecomputer.
 3. The system as in claim 2, wherein said first regionoccupies from substantially 5% to substantially 40% of the local memoryof each said computer.
 4. The system as in claim 3, wherein said firstregion occupies from substantially 10% to substantially 30% of the localmemory of each said computer.
 5. A method of partitioning an independentlocal memory of each computer of a multiple computer system comprising amultiplicity of computers each interconnected via a communicationssystem and each executing a different portion of an applications programwritten to be executed on only a single computer, said method comprisingthe step of: (i) for each said computer partitioning the independentlocal memory into an allocated application memory, said allocatedapplication memory further partitioned into two regions, a first one ofsaid regions comprising application memory contents replicated in atleast on other of said computers, and the second of said regionscomprising application memory contents not replicated in any other ofsaid computers, (ii) transmitting via said communications networkchanges to the replicated content of memory in the first region of theallocated application memory of any one of said multiple computers tothe corresponding replicated memory of at least one other of saidmultiple computers, and (iii) changing the partition between said firstand second region with time by transmitting via said communicationsnetwork additions and/or deletions to the memory locations in the firstregion of the allocated application memory of any one of said multiplecomputers to the first region of at least one other of said multiplecomputers.
 6. The method of claim 5, further comprising: (iv) allocatingless than substantially 50% of the allocated application memory of eachsaid multiple computer to said first region.
 7. The method as in claim6, including the step of: (v) allocating from substantially 5% tosubstantially 40% of said allocated application memory to said firstregion.
 8. The method as in claim 7, including the step of: (vi)allocating from substantially 10% to substantially 30% of said allocatedapplication memory to said first region.